
import {
	Blob,
	btoa,
	createImageBitmap,
	CSSStyleDeclaration,
	performance,
	document,
	DOMParser,
	EventTarget,
	fetch,
	Headers,
	HTMLCanvasElement,
	Image,
	HTMLImageElement,
	ImageBitmap,
	location,
	navigator,
	Request,
	requestAnimationFrame,
	cancelAnimationFrame,
	Response,
	URL,
	window,
	self,
	WebAssembly,
	Worker,
	XMLHttpRequest,
	ImageData,
	TextDecoder,
	core
	} from 'dhtml-weixin';
import { tslFn } from '../../shadernode/ShaderNode.js';

const F_Schlick = tslFn( ( { f0, f90, dotVH } ) => {

	// Original approximation by Christophe Schlick '94
	// float fresnel = pow( 1.0 - dotVH, 5.0 );

	// Optimized variant (presented by Epic at SIGGRAPH '13)
	// https://cdn2.unrealengine.com/Resources/files/2013SiggraphPresentationsNotes-26915738.pdf
	const fresnel = dotVH.mul( - 5.55473 ).sub( 6.98316 ).mul( dotVH ).exp2();

	return f0.mul( fresnel.oneMinus() ).add( f90.mul( fresnel ) );

} ); // validated

export default F_Schlick;
